Adjustment with reference gases - GM70

GM70 User Guide

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For the adjustment procedure with gases, you need the probe that is going be adjusted, accurate reference gas(es), a pressure regulator, a flow meter, a field check adapter (can be ordered from Vaisala) and flexible tubing with 3 mm (1/8 in) inner diameter. For information on available accessories and ordering, see Spare parts and accessories.

Reference gases

To achieve reliable results, reference gases must be traceable to appropriate standards (for example NIST).

  • If adjustment is done by using 1 reference gas (1-point adjustment), the concentration of the gas must be near to the concentration values in which the device is used.
    When adjustment is done only in 1 point, this results in high accuracy only near to the adjustment point, not necessarily over the whole measurement range.
  • When using 2 reference gases (2-point adjustment), the reference gas concentrations should represent the low-end and the high-end of the measuring range. The low-end concentration should be less than 20 % of the measuring range of the probe. The 0 gas can be N2 gas with a purity of N5.0 (or better). The high-end gas can be mixture of CO2 and N2 with concentration near to the upper limit of the measuring range, being 110 % of the range at maximum. Accuracy of the concentrations should be 1 % (or better). Difference between the reference gas concentrations should be more than 20 % of the measuring range.